New evidence, however suggests that onemicrobe sometimes uses the codon UGA as a stop codon and sometimes use it to code for the amino acid pyrrolysine. “The UAG codon is like a fork in the road, where it can be interpreted either as a stop codon or as a pyrrolysine residue,” Shalvarjian said in a press statement. However, when less of it was around, UAG often acted as a stop codon, which yields a different protein entirely. Additionally, scientists could experiment with introducing a similar level of imprecision into gene therapies, which could address maladies caused by premature stop codons (such as cystic fibrosis). “This really opens the door to finding interesting ways to control how cells interpret stop codons,” Nayak said.